Comments

If you install new brake pads on old rotors that don't have the proper finish the brakes can make noise. And if the brake rotor finish is really messed up the noise will probably get worse and the brake pads will wear out quicker.

If this isn't an everyday vehicle you'll be good for now. But eventually the rotors will warp from poor friction material contact. When this happens replace both the brake pads and rotors.

So the for the sake of my wife who insists she knows better than me... driving with bad rotors results in a quicker wear time for brake pads and possibly more wear on rotors that already need to be replaced... other than that (generally speaking) nothing else is impacted?

Because of the poor friction material contact the brakes are going to run hotter. This is what causes the rotors to warp. It's possible the brakes can get so hot where it damages the calipers. But when brakes get this hot you can usually smell it.

So other than that, the only things effected are the brake pads and rotors.

A lot depends on just how "bad" the rotors are..If they are really ripped up, badly scored, the new pads will QUICKLY wear out and your braking ability greatly reduced because of the over-heating and poor pad contact. Sometimes you can get away with minor scoring, but the pads will still wear quickly and it takes a while for the pads to "wear in" (to the uneven surface) and until that happens, braking is poor...Noise and rumble and squealing is to be expected..

What does "bad rotors" mean? Are they rusted? Are they worn below specs? Are they warped causing uneven braking?

The new pads will wear quicker on used rotors since the rotors are "grooved". As long as you stop reasonably quickly you should be ok. If you have extemely long stopping distances and poor braking performance then you are due for new rotors.

After about 200 miles your new pads and old rotors should be mated up as best as they ever will. If you have decent braking performance at that point you should be ok until you need another new set of pads.

Thin rotors can warp easily. They also don't transfer heat as well and that degrades stopping heavy loads, on hills, and in emergency panic stops. As it is, you car is less safe than it could be. It is hard to tell if you are unsafe to the point of dangerous.